An autonomous vehicle is often configured to follow a trajectory based on a computed driving path. However, when variables such as obstacles are present on the driving path, the autonomous vehicle must perform control operations so that the controlled vehicle may be safely driven by changing the speed or the driving path to avoid the obstacles. In many cases, data from cameras can be used to detect obstacles (e.g. other vehicles) in the path. In other cases, radar or LIDAR data can be used. LIDAR is a surveying method that measures distance to a target by illuminating that target with a pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital representations of the target.
Such a vehicle-mounted radar or LIDAR apparatus can be used with automatic cruise control systems, which operate to detect a lead vehicle (e.g., a vehicle positioned ahead and in the same lane as the controlled vehicle). Conventional cruise control systems are configured to cause the controlled vehicle to maintain a constant speed or a speed that keeps constant the following distance to the lead vehicle. However, traditional cruise control systems that only consider the speed of the controlled vehicle or the distance between the lead vehicle and the following vehicle might fail to react quickly enough to changes in the operation of the lead vehicle, thereby causing an unsafe separation between the two vehicles.